import { Injectable } from '@angular/core'
import { Hero } from './hero'
import { HttpClient, HttpHeaders } from '@angular/common/http'
import { Observable, of } from 'rxjs'
import { MessageService } from './message.service'
import { catchError, map, tap } from 'rxjs/operators'
const httpOptions = {
  headers: new HttpHeaders({
    'Content-Type': 'application/json'
  })
}

@Injectable({
  providedIn: 'root'
})
export class HeroService {
  constructor(
    private http: HttpClient,
    private messageService: MessageService
  ) {}
  private heroesUrl = 'api/heroes'
  getHeroes(): Observable<Hero[]> {
    return this.http
      .get<Hero[]>(this.heroesUrl)
      .pipe(
        tap(heroes => this.log('fetched heroes')),
        catchError(this.handleError('getHeroes', []))
      )
  }
  getHero(id: number): Observable<Hero> {
    const url = `${this.heroesUrl}/${id}`
    return this.http.get<Hero>(url).pipe(
      tap(_ => this.log(`fetched hero id=${id}`)),
      catchError(this.handleError<Hero>(`getHero id=${id}`))
    )
  }
  updateHero (hero: Hero): Observable<any> {
    return this.http.put(this.heroesUrl, hero, httpOptions).pipe(
      tap(_ => this.log(`updated hero id=${hero.id}`)),
      catchError(this.handleError<any>('updateHero'))
    )
  }

  addHero (hero: Hero): Observable<Hero> {
    return this.http.post<Hero>(this.heroesUrl, hero, httpOptions).pipe(
      tap((hero: Hero) => this.log(`added hero w/ id=${hero.id}`)),
      catchError(this.handleError<Hero>('addHero'))
    )
  }

  deleteHero (hero: Hero | number): Observable<Hero> {
    const id = typeof hero === 'number' ? hero : hero.id
    const url = `${this.heroesUrl}/${id}`
    return this.http.delete<Hero>(url, httpOptions).pipe(
      tap(_ => this.log(`deleted hero id=${id}`)),
      catchError(this.handleError<Hero>('deleteHero'))
    )
  }

  searchHeroes (term: string): Observable<Hero[]> {
    if (!term.trim()) {
      return of([])
    }
    return this.http.get<Hero[]>(`${this.heroesUrl}/?name=${term}`).pipe(
      tap(_ => this.log(`found heroes matching "${term}"`)),
      catchError(this.handleError<Hero[]>('searchHeroes', []))
    )
  }
  private log(message: string) {
    this.messageService.add(`HeroService: ${message}`)
  }
  private handleError<T>(operation = 'operation', result?: T) {
    return (error: any): Observable<T> => {
      // TODO: send the error to remote logging infrastructure
      console.error(error) // log to console instead

      // TODO: better job of transforming error for user consumption
      this.log(`${operation} failed: ${error.message}`)

      // Let the app keep running by returning an empty result.
      return of(result as T)
    }
  }
}
